It is said that one out of 20 to 30 people suffer from depression including mild cases. Further, many people are troubled with a depressive state which is one of the after effects of cerebrovascular lesion or the like. The depressive state and depression can be thus counted among modern diseases.
For the remission of depression or depressive state, tricyclic antidepressants such as imipramine and amitriptyline have been used heretofore. However, tricyclic antidepressants are not preferred, since they are not effective on nearly 40% of the patients and have harmful side effects which hinder their administration to, particularly, aged people, such as tachycardia, hypotension, headache, finger trembling, constipation and dysuria.
On the other hand, it is known from old times that monoamine oxidase (hereinafter referred to as MAO) inhibitors have an antidepressant effect and it has been pointed out that the range of their effect thereof is wider than that of the tricyclic antidepressants. However, hydrazide MAO inhibitors are now not used, since it was found that they caused hepatic disorders, while non-hydrazide MAO inhibitors have come to be scarcely used, since their MAO inhibition effect is irreversible.
After further investigations, it has been found that MAO is classified into two types, i.e. types A and B, and that harmful side effects such as orthostatic hypotension, headache and dizziness and the so-called cheese effect which causes a hypertensive fit by the interaction with foods having a high tyramine content are caused mainly by the MAO-B inhibition effect.
After extensive investigations made for the purpose of finding functions showing reversible effects while being free from serious harmful side effects or interaction with foods and effective on patients in a wide range under these circumstances, the inventors have noted a MAO-A inhibition effect and made further investigations on compounds having such an effect.
As a result, the inventors have found that the object can be attained by oxazolidone derivatives which will be described below. The present invention has been completed on the basis of this finding.
Although oxazolidone derivatives useful as medicines are disclosed in, for example, Japanese Patent Publication-B Nos. 40428/1985, 5391/1988, 54710/1988, 63671/1988, 56071/1989, 37354/1990, 61465/1990 and 9106/1991 and Japanese Patent Publication-A No. 63671/1988, they are different from the compounds of the present invention in the structure.